The field of data communications typically uses transceivers, or modems, to convey information from one location to another. Digital Subscriber Line (DSL) technology now enables transceivers to communicate rapidly large amounts of data. Transceivers communicate by modulating a baseband signal carrying digital data, converting the modulated digital data signal to an analog signal, and transmitting the analog signal over a conventional wire using techniques that are known in the art. These known techniques include mapping the information to be transmitted into a signal space constellation and slicing the received constellation to recover the transmitted information. The constellation can include both analog and digital information or only digital information.
In the above mentioned communications environment, it is possible that some of the transmitted information could be lost or corrupted. In that event, it is desirable to have a means for error detection and correction. Forward error correction is one well known method of achieving error detection and correction. Error correction codes can be, for example, block codes, cyclic codes, convolutional codes and Viterbi codes.
Reed-Solomon (RS) coding is a widely used cyclic, block coding scheme, particularly suited to demanding applications such as terrestrial broadcasting of digital television, deep space communications, compact disk storage, and data communications over terrestrial lines. RS codes are multi-level codes where the code words are constructed from symbols from a Galios (finite) Field. The code words have the property that is 2 t parity symbols are added to each data word to form a code word, then the code can find and correct up to any t lost symbols. Conventional RS coding requires the use of in-band framing bytes added to the code in order to insure alignment of the RS frame. One of the drawbacks of the aforementioned technique is that the use of in-band framing is wasteful of bandwidth and requires additional circuitry.
Thus, it would be desirable to develop a system in which RS forward error correction may be employed without the need of transmitting additional framing bytes.